Multiarticle press with hydraulically biassed lower rams

ABSTRACT

A MULTIARTICLE PRESS FOR CERAMIC GOODS HAS LOWER, HYDRAULICALLY BIASSED RAMS WHICH ARE CONNECTED WITH A SOURCE OF HYDRAULIC BIASSING PRESSURE VIA A SHUTTLE PISTON IN ORDER TO LEAD DOWNWARDS MOVEMENT OF THE RAMS.

Oct. 12-, 1971 (HERSBERG ETAL 3,611,517

MULTIARTICLE PRESS WITH HYDRAULICALLY BIASSED LOWER RAMS Filed April 25, 1969 2 Sheets-Sheet 1 Fig. 1

IN V EN TORS D v MK? flrroalvavt Oct. 12, 1971 ER$BER EI'AL MULTIARTICLE PRESS WITH HYDRAULICALLY BIASSED LOWER RAMS Filed April 25, 1969 2 Sheets-Sheet 2 Jrraxua r;

vs. CI. 25-91 7 Claims ABSTRACT OF THE DISCLOSURE A multiarticle press for ceramic goods has lower, hydraulically biassed rams which are connected with a source of hydraulic biassing pressure via a shuttle piston in order to lead downwards movement of the rams.

'In the pressing of dry ceramic material, hydraulic presses have been widely accepted. However, they have the disadvantage that they operate comparatively slowly. Therefore in factories in which large batches of goods are prepared, such as tiles or stoneware articles, a number of articles are pressed simultaneously in a single press. Thus, for example, a hydraulic press is used to produce four tiles, each for example measuring 150 by 150 mm., simultaneously. In the case of tiles measuring 100 by 100 mm. nine tiles can be pressed with a single pressing in apress of the same size as above.

However, this manner of operating the press has disadvantages which make themselves felt when the product has to meet high quality standards. It is not possible to i apply the same pressing force to four, six or nine pressings simultaneously, and owing to deformation of the press or the pressing tools on the one hand, or due to inaccuracies in the metering of the material for placing in the press, on the other hand, some of a series of pressings produced simultaneously have a better quality while others are lower in quality. By changing the press design, for instance by including means for setting the moulds or changing their shapes, the effects of deformation of the press and the pressing tools can be reduced. However, it is often ditficult to carry out such measures in the ceramic factories where the press is used and still produce satisfactory results. It is even more difficult to fill each mould to precisely the same extent under all conditions of operation.

One known measure, for instance, is to mount the lower rams of the press which support the articles during pressing on elastic underlays or to press them against elastic material; These measures compensate for unevenness in the amount of material placed in the press for each article. An elastic underlay allows the mould part above it to yield so that the pressing ofthe article in the mould is carried out with the same specific pressure as that of the other articles. Differences in the amount of material charged into the mould are then reflected in small inaccuracies in thickness, which, however, are not so deterimental as an unevenness in the pressing pressure.

It was obvious to apply this principle of an elastic intermediate layer between a lower mould part and the lower press platen for equalizing pressing forces in neighbouring moulds. However, such a construction was only made for small sizes, that is to say about 20 by 20 mm. The properties of the elastic material made the method unsuitable for larger sizes.

The present invention consists in an apparatus for the simultaneous pressing of articles comprising upper plungers, lower hydraulic rams for supporting the articles United States Patent "ice during the pressing, hydraulic biassing means for pressurising the lower rams so as to allow them to yield in a downward direction during pressing and return thern to their upper positions at the end of pressing, a cylinder hydraulically connected with the rams and with the hydraulic biassing means, and a shuttle piston in the cylinder for limiting fiow of hydraulic liquid, between, on the one hand, the lower rams and, on the other hand, the hydraulic biassing means.

A pressing apparatus in accordance with the invention can be used to achieve precisely the same pressing pressure on each mould, more particularly in the case of medium and large sizes of ceramic goods. It is additionally possible to use elastic layers between the lower rams and a lower platen of the press in order to compensate for errors in the filling of the individual moulds between the upper plungers and the lower rams. The invention is applicable both to hydraulic presses in which the upper plungers are moved hydraulically and presses in which they are moved mechanically.

The shuttle piston can be a differential piston with opposite active faces of different areas, the small face being connected with the lower rams.

Additionally the apparatus can comprise a duct connecting the two faces of the shuttle piston hydraulically, and flow limiting means, for instance a check valve, in this duct.

In order to prevent damage to the check valve owing to high pressures, the apparatus can comprise a sliding valve part arranged to be positively driven by the shuttle piston and to shut off the lower rams from the check valve hydraulically as the shuttle piston is moved by the rams during their downward travel.

The apparatus can comprise mechanical means such as springs for holding the lower rams in their raised positions.

One embodiment of the invention is now described with reference to the accompanying drawings.

FIGS. 1 and 2 represent longitudinal sections through a pressing apparatus embodying the invention with a control or shuttle piston in two working positions.

FIGS. 3 and 4 show a different form of shuttle piston arrangement in two working positions.

The press or pressing apparatus shown in the figures comprises a vertically moving upper press platen 1 (FIG. 1) carrying upper rams or plungers 2 which are pressed downwards on to material 3 to be pressed tilled in the mould cavities 5 of the stationary mould part 4. The lower rams 6 are carried by piston 7 which in a conventional manner are carried in a cushioning part or base 8. The pistons are provided with sealing piston rings 9. The cavity 10, common to all the pistons 7, in the base 8 is filled with a suitable hydraulic liquid such as a hydraulic oil or water. The constant biassing pressure of the hydraulic liquid forces the pistons 7 upwards so that their upper shoulders 11 about against the cover plate -12 of the base. The cylinder space 10 common to the pistons 7 is connected by the duct 13 with the cylinder space 14 of the control or shuttle piston 15. The shuttle piston is in the form of a difierential piston with opposite active faces of different areas. The larger face or side 19 of the diiferential piston 15 is pressurised by a source (not shown) of biassing hydraulic pressure. This source of pressure is also connected by the bypass duct 16 and the check valve 17 with the cylinder space 14 adjoining the smaller end of the piston. Owing to the difference in areas of the two ends of the piston, the latter is pressed against the shoulder 18 (i.e., towards the left in FIG. 1) by the biassing hydraulic liquid pressure.

In a pressing operation (see more especially FIG. 2) the lower rams 6 and the piston 7 are moved downwardly by the upper rams 2 against the opposing biassing pressure and hence their upper shoulders 11 cease to be in contact with the plate 12. During this movement part of the hydraulic liquid is displaced from the common space through the duct 13 into the cylinder space 14 and shifts the control piston 15 against the biassing pressure applied to its larger face 19 until the shuttle piston comes to abut against the end plate 20 of the cylinder 21. Flow of hydraulic liquid in the duct 16 is prevented by the check valve 17.

In the cylinder space 14 and the cylinder space 10 in the base 8 and the duct 13 connecting them a pressure obtains which rises as the force of the press is taken up by the lower rams 6 and the pistons 7 and the masses of material are pressed. If one pressing should be thicker than another owing to a larger quantity of material being filled into one of the moulds there will be no effect on the force with which such mould and material are pressed. The only result will be that the respective lower ram and piston will be forced somewhat further down. The pressing force will be therefore the same for all pressings.

When at the end of the pressing the platen 1 with the plungers 2 is raised again, the pressure on the smaller face of the shuttle piston 15 is relieved and hence the biassing pressure acting on the face 19 of the shuttle piston moves the piston against the abutment face or shoulder 18 again and the hydraulic liquid displaced from space 14 passes through duct 13 so as to raise the pistons 7 back into their original positions. Any loss due to leakage will be made up for by hydraulic liquid passing through duct 16 and check valve 17, so that the shoulders 11 of all the pistons rest against the cover or lid 12 of the base 8.

In order to bias the pistons 7 and the lower rams 6 upwardly to their raised position and ensure that they are in the raised position at the beginning of pressing, nonhydraulic means, such as compression springs 25, can additionally be provided. 1

The hydraulic pressures used for tile production (an idle pressure of 50 kg./cm. at an actuating pressure of 500 kg./cm. or more, in accordance with the dimensions of the pistons) may excessively load the check valve. Therefore in accordance witha further embodiment of the invention, as shown in FIGS. 3 and 4, a cut-01f valve means comprising valve slide 22 is secured to and arranged to be positively driven by the shuttle piston 15 and to close the connection between the duct 13 and the check valve 17 as soon as the shuttle piston 15 has begun its movement to the right during pressing. In this manner the check valve 17 is not subjected to the pressing pressure obtaining in the space 10.

We claim:

1. An apparatus for simultaneously pressing of a plurality of articles from a material such as ceramic material, comprising a plurality of vertically movable upper plungers; a movable platen secured to all of said upper plungers to effect simultaneous vertical movement of said upper plungers; a stationary mould part having a plurality of mould cavities each respectively aligned and cooperating with one of said upper plungers; a plurality of lower rams respectively disposed in each of said mould cavities below the material being pressed, each of said lower rams being individually vertically movable between upper and lower positions, and being slidably received at its lower ,4 end within a respective fluid cylinder, all of said fluid cyinders beingv in fluid communication with each other; a shuttle cylinder having an enlargeddiameter first end connected to a source of fluid under pressure and a reduced-diameter second end; a shuttle piston slidably disposed in said shuttle cylinder between said first and second ends and having respective enlarged-diameter and reduced-diameter portions in said first and second ends of said shuttle cylinder; and duct means communicating said second end of said shuttle cylinder with said fluid cylinders; said fluid cylinders, said reduced-diameter second end of said shuttle cylinder, and said duct means being filled with hydraulic liquid, said shuttle piston being shiftable away from said duct means responsive to fluid pressure in said duct means resulting from downward movement of said upper plungers and said lower rams.

2. An apparatus as defined in claim 1, further comprising a stationary abutment, each of said lower rams having an upper shoulder adapted to .abut against said abutment when said lower ram is in its uppermost position, the hydraulic liquid biasing each of said lower rams upwardly against said abutment.

3. An apparatus as defined in claim 2, further comprising a bypass duct communicating said duct means directly with the source of fluid under pressure around said shuttle cylinder, and flow limiting means disposed in said bypass duct to permit fluid flow from the source of fluid under pressure to said duct means while preventing fluid flow in the opposite direction, whereby any fluid lost from said fluid cylinders or said duct means will be automatically replaced from the source of fluid under pressure through said bypass duct.

4. An apparatus as defined in claim 3, further comprising cut-oif valve means secured to said shuttle piston and disposed between said flow limiting means and said duct means, and adapted to cut off fluid communcia-tion therebetween when said shutle piston is shifted away from said duct meansresponsive to fluid pressure in said duct means, to thereby preclude damage to said flow-limiting means resulting from excessive fluid pressure in said duct means.

5. An apparatus in accordance with claim 3 in which said flow limiting means is a check valve.

6. An apparatus in accordance with claim 5, further comprising mechanical means for biasing said lower rams towards their upper positions.

7. An apparatus in accordance with claim 6 in which said mechanical means comprise a plurality of compression springs each engaging one of said lower rams.

References Cited UNITED STATES PATENTS 8/1960 Great Britain 164173 ROBERT D. BALDWIN, Primary Examiner U.S. Cl. X.R. 

